Arm in Cross Section – Anatomy of the Arm

00:01 In this lecture we are going to look at the arm. So we are going to start off by looking at the arm in cross section and returning to the brachial fascia we spoke about. We will also look at how it forms the intermuscular septae. We will then look at the anterior compartment, the biceps brachii, brachialis and coracobrachialis muscles and some neurovascular relations in the anterior compartment. We will then look at the cubital fossa that lies directly anterior to the elbow joint, its boundaries and the contents and then we will finish by looking at the posterior compartment, specifically triceps brachii and again some neurovascular relations. So if we look at the compartments of the arm to start within, this is a section through the arm and we can see that we have got the humerus here and then lying anteriorly we have got this surface here where we have got a subcutaneous tissue and the superficial fascia and then we have got this line here that is running around the muscles and that is the brachial fascia. So we are going to look at that in a bit more detail.

01:12 When looking at cross sections, it is important to realize as this diagram here indicates that we are actually looking at it from below. So here we are looking at it from below.

01:22 So this is the medial aspect here, this is the lateral aspect, this is the posterior aspect and this is the anterior aspect. So the transverse section of the arm reveals the brachial fascia forms two muscular compartments. It does this by way of the lateral intermuscular septum and the medial intermuscular septum. So what we can see here is the humerus and then on the outside we have got the brachial fascia. We can see the brachial fascia dives deep here laterally into the depths of the arm and attaches to the humerus. We can also see similar here, where we have the brachial fascia running around the outside and then we have got this medial intermuscular septum running in head. And that creates two compartments contain the anterior compartment and it contains the posterior compartment. The anterior compartment is the flexor compartment. The posterior compartment is the extensor compartment. So they flex the elbow joint and they extend the elbow joint muscles in these compartments.

02:37 Importantly though it's important to remember that some of these muscles also act on the glenohumeral joint as we will see. So the majority of the muscles in the arm do act on the elbow joint and principally there are two types of movements. We have flexion and extension. We also have pronation and supination. So the muscles we have in the arm act on the elbow joint and they also act on the radio-ulnar joints which like pronation and supination to work out.

03:10 So we will come back to this, as we progressed through the course.